Trie from list of words in Purescript

wordztrie.purs

module Main where

import Prelude (($))
import Data.Map (Map, empty, lookup, insert)
import Data.Ord (class Ord)
import Data.String (toCodePointArray, CodePoint)
import Data.Foldable (foldl)
import Data.Maybe (fromMaybe)
import Data.List (List(..), (:), fromFoldable)

data Trie a = Trie (Map a (Trie a))

emptyTrie :: ∀ a. Trie a
emptyTrie = Trie empty

makeTrie :: ∀ c. Ord c => List c -> Trie c -> Trie c
makeTrie (Nil) trie = trie
makeTrie (x : xs) (Trie t) = Trie (insert x subtrie t)
    where subtrie = makeTrie xs $ fromMaybe emptyTrie $ lookup x t

wordz :: List String -> Trie CodePoint
wordz xs = foldl f emptyTrie xs
  where f t s = makeTrie (fromFoldable (toCodePointArray s)) t